1. Global Warming in Geologic Time David Archer University of Chicago

2. Joseph Fourier Memoires d l’Academie Royale des Sciences de l’Institute de France VIIII, 570-604 (1827) Joseph Fourier described the greenhouse effect in 1827

3. T earth = 259 K = -14° C = 6°F Energy Balance of a Bare Rock

4. T atm = 259 K T earth = 303 K = 86° F A Planet with an Atmosphere

5. John Tyndall, 1859 John Tyndall discovered that CO 2, H 2 O, and CH 4 are greenhouse gases. O 2 and N 2 are not.

6. CO O Symmetric Stretch Asymmetric StretchBend CO O C O O COO Resting State No Resting DipoleIR Inactive 2349cm 660cm CO 2 is a greenhouse gas

7. Water vapor is a greenhouse gas

8. Earth’s outgoing infrared spectrum

9. The band saturation effect

10. Svante Arrhenius Svante Arrhenius calculated that doubling CO 2 would warm the Earth by 4-6°C, in 1896

11. The water vapor feedback

12. The ice albedo feedback

13. Intense warming in high latitudes because of ice-albedo feedback

14. David Keeling David Keeling started measuring CO 2 concentration in the atmosphere

15. 300 310 320 330 340 350 360 370 380 390 400 A t m o s p h e r i c p C O 2, p p m Mauna Loa, Hawaii

16. IPCC IPCC predicted in 1990 that global warming would rise above the noise by 2000

17. IPCC IPCC in 1995 found a “discernable human influence on global climate”

18. Only greenhouse gas forcing looks like the recent temperature rise. Climate forcings Crowley, 2000

20. What about phenomena undreamed-of? The sun is good at pushing our climate buttons. Clouds? Humidity? “They blame CO 2 because they can’t think of anything else.”

21. A detective story The Butler. Found holding a smoking gun next to the deceased. Forensics matches the gun with the bullets. The Chauffer. In Kentucky for sister’s wedding. “Can’t think of any way he could have done it.” To convict the Chauffer, we’d have to first unconvict the Butler.

22. Airborne Fraction of Carbon Released Century timescale peak Millennial timescale tail What happens to fossil fuel CO 2

23. One gallon of gasoline Usable energy: 2500 kcal Unwanted greenhouse energy over CO 2 lifetime:

24. One gallon of gasoline Usable energy: 2500 kcal Unwanted greenhouse energy over CO 2 lifetime:100,000,000,000 kcal

25. Avoiding Dangerous Climate Change If the peak contains 50% of the emitted CO 2, and climate sensitivity  T 2x = 3° C, then we could emit ~ 700 Gton C and avoid warming greater than 2° C. We have already emitted 300 Gton C. Oil + Gas ~ 400 Gton C. Just stop burning coal.

26. How Long will Global Warming Last? IPCC 2001 and earlier reports implied that global warming would last about a century.

27. “Carbon dioxide cycles between the atmosphere, oceans andland biosphere. Its removal from the atmosphere involves arange of processes with different time scales. About 50% of a CO2 increase will be removed from the atmosphere within 30 years, and a further 30% will be removed within a few centuries. The remaining 20% may stay in the atmosphere for many thousands of years.” IPCC 2007 Summary for Policymakers

28. 4000-5000 Gton C Release Peak 1 kyr 10 kyr CLIMBER67%57%26% Archer 200560%33%15% Lenton 200667-75%14-16%10-15% Ridgwell subm.50%34%12% Tyrell 200770%42%21% Atmosphere / Ocean / Weathering / CaCO 3 models Airborne Fraction

29. 1000-2000 Gton C Release Peak 1 kyr 10 kyr CLIMBER45%31%14% Archer 200558%24%11% Lenton 200650-63%17-19%11% Atmosphere / Ocean / Weathering / CaCO 3 models Airborne Fraction

30. Warming for the Long Haul 100010,000 yearsyearsfrom now 2000 Gton C3° C1.5° 5000 Gton C5°3°

31. 3 °C Year A.D. Northern Hemisphere Average Temperature How much is 3 °C? 10002000

32. So What Part I: Sea Level -150 -100 -50 50 100 Sea Level, m Last Glacial Maximum 20kyr ago Eocene 40Myr ago Today Pliocene 3 Myr ago -10-505 Global T Change, °C

33. So What Part I: Sea Level -150 -100 -50 50 100 Sea Level, m Last Glacial Maximum 20kyr ago Eocene 40Myr ago Today IPCC Forecast for the year 2100 Pliocene 3 Myr ago -10-505 Global T Change, °C

34. So What Part I: Sea Level -150 -100 -50 50 100 Sea Level, m Last Glacial Maximum 20kyr ago Eocene 40Myr ago Today Eventual Sea Level Rise? Pliocene 3 Myr ago -10-505 Global T Change, °C

35. Message to Florida: 20 meters would be it for ya’ll

36. Ice flows if there’s water at the bed It takes thousands of years to respond to climate changes. Ice sheet models

37. Melt water carries heat quickly We don’t know how water gets through the ice The real Greenland ice sheet responds in a few months. Real ice sheets

38. A moulin in Greenland where water submerges into the ice. Zwalley et al (2002)

39. Earthquakes under Greenland ice Ekstrom et al., 2006

40. Heinrich Events 30-70 kyr ago Ice Rafted Debris (layers of rocks in ocean sediments) Ice sheet collapsed into the ocean Raised sea level ~5 m in a few centuries. Could the Greenland ice sheet start doing this?

41. Meltwater Pulse 1A 14 kyr ago 1.5 to 3 Greenlands in 1-5 centuries. We’re not even sure where this water came from.

42. 5000 Gton of C release (business-as-usual to 2100 then stop) 50 m sea level rise, eventually 3.5% of the land area, home to >10% of the world’s population Every American ultimately inundates 1000 sq. ft. of land per year. A long-term sea level scenario

43. The Next Ice Age 3002001000 22° 23° 24° 25° Intense Seasons in the Southern Hemisphere Intense Seasons in the Northern Hemisphere Precession Cycle Angle from the Pole to the Orbit Obliquity Cycle Eccentricity Cycle 5% Elliptical, 95% Circular 100% Circular Thousands of Years Ago L o w E c c e n t r i c i t y W e a k P r e c e s s i o n

44. A Threshold Model sunlight Interglacial Climate State

45. A Threshold Model Interglacial Climate State summer sunlight gets weak

46. A Threshold Model summer sunlight gets weak winter snow survives the summer an ice sheet is born Glacial Climate State

47. A Threshold Model sunlight gets strong again Ice reflects light back to space ice persists Glacial Climate State

48. Dim Northern Hemisphere Sun = Growing Ice

49. CLIMBER Model Nucleates an Ice Sheet Trigger

50. 400 410 420 430 440 450 460 470 100200300400500600 CLIMBER model, Archer and Ganopolski, 2005 Critical Insolation Value, W/m 2 Atmospheric pCO 2 If CO 2 is higher, it takes a colder sun to nucleate the ice sheet.

51. Natural: Near miss! Wait until 50 kyr Archer and Ganopolski, 2005

52. 1000 Gton: Wait until 130 kyr from now

53. 5000 Gton: No glaciation for 400 kyr

56. Conclusions Global warming is well understood, it has been detected, and the forecast for the end of the century is frightening. CO 2 emission will continue to effect climate for hundreds of thousands of years into the future. Sea level may ultimately rise 100 times more than the forecast for the year 2100.